Aluminum alloys combine low density with structural strength and crash resistance, which makes them attractive for production of structural and body parts in the motor vehicle industry. However, aluminum alloys have lower formability compared to draw-quality steel. In some cases, relatively low formability of the aluminum alloys can lead to difficulties in obtaining good part designs and create problems with failure due to fracture or wrinkling. Warm forming of aluminum alloy sheets is used in the motor vehicle industry to overcome these challenges since the aluminum alloys exhibit increased formability at elevated temperatures. Generally, warm forming is the process of deforming metal at an elevated temperature. Warm forming can maximize the metal's malleability but can create its own challenges. In some cases, heating may negatively affect mechanical properties of an aluminum alloy sheet. Heated aluminum alloy sheets may exhibit decreased strength during the stamping operations, and the decreased strength characteristics may persist after cooling of the alloy sheet. Heating of the aluminum alloy sheets also can lead to increased thinning of the aluminum alloy parts during stamping operations. For example, heating of an aluminum alloy facilitates precipitation and dissolution processes within the alloy, which may lead to re-crystallization and grain growth that may change the alloy's structure and negatively affect its mechanical properties. The above processes are known to occur in hardened aluminum alloys, for example, 6XXX series alloys in T6 or T61 temper, leading to decreased strength characteristics.
Heat treatable, age-hardenable aluminum alloys, such as 2XXX, 6XXX and 7XXX aluminum alloys, which are often used for the production of panels in motor vehicles, are typically provided to the manufacturer in the form of an aluminum sheet in a ductile T4 temper, in order to enable the manufacturer to produce desired automotive panels by stamping or pressing. To produce functional motor vehicle parts meeting the required strength specifications, parts produced from an aluminum alloy in T4 temper are typically heat treated post-production and subsequently age hardened, naturally or artificially, to increase their strength. For example, 6XXX aluminum alloys may be artificially aged at the elevated temperature to convert the aluminum alloy into T6 or T61 tempers. Hardened aluminum alloys have decreased formability, which negatively affects the manufacturers' ability to shape them. It is desirable to improve these alloys' formability, for example, by elevating their temperature without negatively affecting their structure and mechanical characteristics.
Accordingly, the manufacturers of aluminum alloy parts are in need of improved warm forming processes for hardened aluminum alloys, such as the alloys in T6 or T61 tempers, to produce the aluminum they use for making parts.